1. Field of the Invention
The invention relates to interfaces, methods, apparatus, and systems for storing data. Specifically, the invention relates to interfaces, methods, apparatus, and systems for managing incremental data storage.
2. Description of the Related Art
Data storage devices and systems are subject to equipment failures, software bugs, operational errors, and disasters that prevent immediate or long term access to valuable data. Additionally, data storage systems often support environments and applications that require storage reliability and availability that is greater than what is inherently provided by individual storage devices. As a result, many techniques and strategies have been applied to data storage devices and systems in order to increase the reliability and availability of data access. Some of those techniques include storage redundancy, data archiving, and remote copy techniques.
Storage redundancy techniques improve reliability by storing redundant images on multiple devices. Data mirroring, in which data is written to two or more devices in parallel, is perhaps the simplest redundancy technique. Although expensive in terms of storage usage, data mirroring facilitates increased performance in that read operations may be distributed to each parallel device to increase storage throughput. However, storage redundancy techniques, although useful, do not address the need for access to previous copies of data files or images within a data storage system.
Data archiving techniques were developed in response to the need to access previous copies of data files or images within data storage systems. With data archiving techniques, data files or images are copied to backup devices and maintained for subsequent use. Backup devices typically comprise slower media that must be carefully managed to successfully restore a file or image to a previous state. To reduce the bandwidth associated with archiving data, incremental techniques are often applied in which only the changes to a file or image are stored on the archive media. Incremental techniques while useful, may increase the complexity of restoring data files or images within data storage systems.
Remote copy techniques are a particular form of data archiving in which data is copied to a remote site either via physical media or transmission links. The availability of a remote copy facilitates recovery operations in the event of a local disaster such as a fire or flood. However, providing complete and constant data availability requires transmission of each write operation to the remote site resulting in high bandwidth requirements for the transmission link.
The aforementioned techniques and strategies are often implemented as host-based solutions requiring considerable planning, administration, and coordination for reliable deployment. Typically, multiple techniques and strategies must be deployed and managed to fit the needs of a particular installation. Such solutions are typically expensive to implement, reduce system performance, and may not provide adequate data availability and reliability.
Consequently, a need for an integrated approach to increasing data availability and reliability that is inexpensive to deploy, easy to manage, and transparent to system performance. In particular, what is needed are interfaces, methods, apparatus, and systems for providing and managing incremental data storage in a manner that supports policy management, data redundancy, and compacted remote copy operations.